Olefin polymerization catalysts are of great use in industry. Hence there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on metallocenes as catalyst precursors, which are activated either with the help of an alumoxane, or with an activator containing a non-coordinating anion.
Useful metallocene catalysts have been based upon bis-indenyl transition metal compounds. In particular, bridged bis-2-substituted indenyl transition metal compounds and bridged bis-2,4-disubstituted indenyl transition metal compounds have found use in polymerizing propylene, see for example U.S. Pat. No. 5,276,208 and EP 576 970.
Also see WO 2011/051705 which discloses substituted indenyl compounds, but no cyclic bridging groups. Also see Ransom, et al. Organometallics (2011), 30(4), pp. 800-814 where a series of ansa-bridged ethylene-bis(hexamethylindenyl)zirconium and hafnium complexes were explored. Likewise, see CN 2006-10080838 (also referred to as CN 101074276 B) which appears to use Me2Si(2-Me-4-iPrInd)2HfCl2 to make isotactic polypropylene with branching by adding in functionalized styrene where the functional group is a vinyl group. See also U.S. Pat. No. 7,741,417; U.S. Pat. No. 7,220,695; and WO 2008/027116 where the processes are disclosed to produce isotactic polypropylene by contacting propylene and optionally one or more monomers with a bis-indenyl Group 4 metallocene compound supported on a silica treated with organoaluminum compound(s) and heterocyclic compound(s), under slurry conditions in the presence of hydrogen at a temperature of about 50° C. to about 160° C. and a pressure of from about 3 MPa to about 5 MPa to provide a catalyst activity of greater than 30,000 lb of product per lb of catalyst (note that rac-dimethylsilyl-bis(2-methyl-4,6-diisopropyl-indenyl)hafnium (or zirconium) dimethyl (or dichloride) are listed in the text).
Also see U.S. Pat. No. 7,385,015 where certain bis-indenyl compounds are supported on a support that has been combined with a first trialkylaluminum, calcined, then combined with a second trialkylaluminum compound(s), where the alkyl groups have two or more carbon atoms and the first and second trialkylaluminum compound(s) may be the same or different. Note that rac-dimethylsilyl-bis(2-methyl-4,6-diisopropyl-indenyl)hafnium (or zirconium) dimethyl (or dichloride) are listed in the text as catalysts that can be supported and dimethylsilylbis(2-methyl-4-phenyl)hafnium dimethyl is used in the examples.
U.S. Pat. No. 7,220,695 and U.S. Pat. No. 7,741,417 disclose supported activators of an ion-exchanged layered silicate, an organoaluminum compound, and a heterocyclic compound, which may be substituted or unsubstituted. Note that rac-dimethylsilyl-bis(2-methyl-4,6-diisopropyl-indenyl)hafnium (or zirconium) dimethyl (or dichloride) are listed in the text as catalysts that can be supported and dimethylsilylbis(2-methyl-4-phenyl)hafnium dimethyl is used in the examples.
See also “Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis-2-methyl-4,6-diisopropylindenyl ligands” Izmer et al., Journal of Organometallic Chemistry (2005), 690(4), pp. 1067-1079 which describes zirconium and hafnium ansa-complexes containing 2,4,6-trialkyl-substituted indenyl fragments, such as rac- and meso-Me2Si(2-Me-4,6-R2C9H3-η5)2MCl2 (R=Me, iPr; M=Zr, Hf) The complexes reproduced below were disclosed. No polymerizations using these compounds were performed.


EP 1 209 165 A2 and U.S. Pat. No. 5,739,366 disclose diphenyl silyl bis(4-isopropyl-2,7-dimethylindenyl) ZrCl2.
U.S. Pat. No. 5,767,033 mentions dimethylsilyl-bis{1-(2-methyl-4-i-propyl-7-methylindenyl)}hafnium dichloride at column 11, line 43 and uses rac-dimethylsilyl-bis{1-(2,7-dimethyl-4-isopropylindenyl)}zirconium dichloride and rac-diphenylsilyl-bis {1-(2,7-dimethyl-4-isopropylindenyl)}zirconium dichloride in the examples. Cyclic bridging groups do not appear to be mentioned.
None of the above disclose hafnium based indenyl metallocene compounds where the 4 position is substituted, the 2 and 3 positions are not substituted, and the bridge is a cyclic group, preferably used in combination with a non-coordinating anion activator.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, to alter comonomer distribution without negatively impacting the resulting polymer's properties, increasing vinyl chain ends, particularly increasing vinyl unsaturations at the chain end while also maintaining or increasing Mw.
It is therefore an object of the present invention to provide novel catalyst compounds, catalysts systems comprising such compounds, and processes for the polymerization of olefins using such compounds and systems.